In conventional bank note processing machines the bank notes generally are singled in a stack and led past a sensor device by means of a transport path. The individual bank notes are checked by sensors of the sensor device and dependent on the checking result are supplied to certain final destinations or stacker units.
For checking the bank notes several sensors can be provided, which judge the bank notes according to different criteria. Accordingly, several stacker units are available, which stack the bank notes of the different categories into units of an adjustable piece number. If for example bank notes of a certain category are to be stacked in units of a piece number of 100 bank notes, it is necessary to perform a separation in the continuous flow of bank notes between the one hundredth bank note and the following bank note meant for the same stacker after the one hundredth bank note has arrived at the stacker.
In connection with this, from DE-PS 34 12 725 it is known to use two stackers for bank notes of the same category. If 100 bank notes are placed in the respectively active stacker, the following bank notes will be supplied to the second identically constructed stacker via a diverter in the transportation system. In this known solution it is necessary to provide two stackers of the same construction and the respective required space.
From EP-OS 0 119 814 is known a solution, which requires only one stacker per bank note category. For this purpose on the stacker is provided a separation element. At first this separation element is in an idle position until, analogously to the above-mentioned example, 100 bank notes have been stacked. After that the separation element is inserted into the flow of bank notes between the one hundredth bank note and the bank note following thereupon in such a way, that the following bank notes are temporarily stored on the separation element. Meanwhile, the stacked unit of bank notes can be emptied. After the emptying the temporarily stored bank notes are stored in the stacker. The separation element returns to its idle position.
This solution has the disadvantage, that with higher transportation speeds a relatively high actuating power for accelerating the separation element has to be summoned, which can only be achieved with a correspondingly high effort. With such a high transportation speed a reliable operation of the stacker cannot be guaranteed.
In DE 44 37 722 A1 it is proposed to interrupt the delivery of bank notes to the transportation system instead, when the sensor device detects that the predetermined piece number of a category has been reached. The bank notes of the same category already singled at this point of time are temporarily stored in the sorter, until the ready stacked bank-note stack has been removed. The temporary storage can be performed in the stacker itself or in a buffer path integrated in the transport path. This solution has the general disadvantage that the machine due to the interruption works in a discontinuous fashion.
In the solution in which the already singled bank notes are stored in the stacker itself, the stacker has the form of a spiral slot stacker, as for example described in DE-OS 32 32 348. However, the stripper for stripping out the bank notes accommodated in the slots of the stacker wheel is designed to be movable in such a way that it can be moved out of the stacker wheel or into the stacker wheel. The components interact with each other in such a way that the movable stripper when moving out of the stacker wheel strips out the one hundredth bank note onto the stack deposit, and that the bank notes located in the next slots of the stacker remain therein. In the meantime, the stacker wheel further rotates and accommodates the bank notes which had already been singled at the point of interruption. As soon as the stack deposit is emptied and prepared for stacking a next bank-note stack, the stripper again is moved into the stacker wheel. Then the stacking operation is continued in the usual fashion.
The disadvantage in this solution is that the stacker wheel has to be stopped, so as to enable the stripper to move again into the stacker wheel. Because with a rotating stacker wheel there exists the danger that the stripper collides with the bank notes located in the slots, before it has reached its strip-out position. However, this means that the transportation system does not only have to be interrupted as soon as the predetermined piece number of a category has been reached, but potentially once again when the stripper is moved back into the stacker wheel.